The diagnostic capabilities of the medical profession have increased significantly throughout the years. One such advancement has been the use of ultrasound to obtain images of internal organs. The ultrasonic waves reflect off of the interfaces of the organs to provide a two dimensional image of the organ on a CRT viewing screen. Ultrasound transducers can be either static, which provide a stationary image, or two dimensional, which provide a moving or real time image. Computerized three dimensional reconstruction of ultrasonic imaging is also possible.
Other uses for ultrasound include the ability to determine flow rate and direction of fluid within vessels of the body. A Doppler ultrasound transducer, combined with a two dimensional transducer is used to determine flow rate and direction. The Doppler transducer, either a pulse or continuous flow Doppler transducer, allows the rate and direction at which blood or other fluids are moving through the veins, arteries or portal vessels of the body to be measured. Color coding of Doppler interrogation is also possible. This information can be used to diagnose blockages or restrictions within the vessel.
The use of ultrasound allows the character and status of certain internal organs and vascular structures to be determined through the use of non-invasive, non-surgical procedures. Two dimensional, real time, transducers provide more information regarding the functioning of certain organs than static transducers and are, therefore, more useful from a diagnostic view point than static transducers.
Ultrasound images are produced by the ultrasound waves reflecting off the surface of soft tissues in the body. Ultrasound waves can penetrate to varying depths, before being deflected. The depth is determined by the frequency at which the transducer transmits the sound waves. Not all waves are reflected however, some pass through the tissue and others are absorbed by the tissue. Since the image is created by the pattern of the reflected waves, the more waves that are reflected, the clearer the image produced will be.
In general, abdominal ultrasonic examinations are conducted with the ultrasound transducer being placed on the outside of the abdominal wall. If the organ to be imaged is close to the surface, it is generally not difficult to obtain a good quality image. However, as the structure of interest lies deeper within the body, or if the patient is overweight or if bowel gas is present the image produced will not be as clear due to absorption of waves by the intervening tissue.
The farther away from the transducer that the organ lies, the fewer waves will reach it and the image will be less and less clear. In addition, if the organ or vessel is shielded, lying behind other organs, the image can also be distorted due the reflection of waves off the intervening tissue, causing tissue imposed attenuation of the image.
These problems cannot be solved by placing the transducer on the patient's back due to the existence of too much bone and muscle tissue, through which the ultrasound waves cannot penetrate.
Other options for use of ultrasound technology include the placement of a static ultrasound transducer on a flexible probe for insertion into the stomach or colon. The static transducer is used to obtain a still picture of the colon, pancreas, biliary tract or esophagus wall. This technique is generally used to obtain images of ulcers, lesions, or tumors on the walls or within the structures.
Doppler transducers are also used as a guiding means on the end of a catheter. The direction of blood flow is determined and used to guide the catheter into the correct blood vessel. Once in position, the required procedure can take place.
None of these procedures provide an apparatus or a method for the two dimensional imaging of the deep or shielded internal organs, or the detection of the flow rate and direction in deep or shielded blood vessels, such as the abdominal aorta and its branches.
There exists, therefore, a need for obtaining high resolution, dynamic imaging of the internal structures lying deep within the body and for obtaining accurate flow rate and direction of vessels which lie deep in the body or which are blocked by organs.